Fan structure

ABSTRACT

A fan includes a blade assembly rotatably supported in a frame. The blade assembly includes a cylinder having an outer surface to which blades are mounted and an inner surface to which magnets are mounted. The blade assembly has an axle concentric with the cylinder. The frame includes a casing made of silicone steel that is fixed inside the frame and supports a bearing device. The bearing device defines a central bore rotatably receiving the axle of the blade assembly therein with the cylinder of the blade assembly fit over and spaced from the casing. Windings of conductive wires are encased and fixed in the casing and surround the bearing device for being electrically powered to generate a magnetic field that interacts with the magnetic means of the blade assembly to rotate the blade assembly. The casing includes opposite upper and lower disks with tabs extending between the upper and lower disks. The tabs extends from a circumference of the upper disk and have free ends fit into corresponding notches defined in the lower disk with a major surface of the tabs extending along a circumferential direction of the disks. Portions of the lower disk project beyond the tabs and are positioned in correspondence to the magnets of the blade assembly for magnetically attracting and thus maintaining the blade assembly in a close position with respect to the lower disk to eliminate “pump” action of the blade assembly.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a fan structure.

[0003] 2. The Related Art

[0004] Fans have been widely used in removing heat from all kinds of devices that generate heat during their operation. Two major concerns of the fans are the noise caused by the operation of the fan and the airflow rate that can be induced by the fan. A conventional fan comprises a fixed frame and a rotary blade assembly rotatably supported in the frame by bearing. To enhance the overall performance of the fan, some particularly designed, sophisticated bearings are employed to reduce noise and to improve efficiency of the fan. However, such sophisticated bearings are expensive and thus increase the overall costs of the fan.

[0005] Thus, it is desired to have a fan structure of low costs but high performance to overcome the above-mentioned problems.

SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide a fan having a simple structure and thus low costs.

[0007] Another object of the present invention is to provide a fan structure having a high performance for efficiently driving airflow.

[0008] A further object of the present invention is to provide a fan structure, which eliminates the axial reciprocation of the fan blade assembly.

[0009] To achieve the above objects, in accordance with the present invention, there is provided a fan comprising a blade assembly rotatably supported in a frame. The blade assembly comprises a cylinder having an outer surface to which blades are mounted and an inner surface to which magnets are mounted. The blade assembly has an axle concentric with the cylinder. The frame comprises a casing made of silicone steel that is fixed inside the frame and supports a bearing device. The bearing device defines a central bore rotatably receiving the axle of the blade assembly therein with the cylinder of the blade assembly fit over and spaced from the casing. Windings of conductive wires are encased and fixed in the casing and surround the bearing device for being electrically powered to generate a magnetic field that interacts with the magnetic means of the blade assembly to rotate the blade assembly. The casing comprises opposite upper and lower disks with tabs extending between the upper and lower disks. The tabs extends from a circumference of the upper disk and have free ends fit into corresponding notches defined in the lower disk with a major surface of the tabs extending along a circumferential direction of the disks. Portions of the lower disk project beyond the tabs and are positioned in correspondence to the magnets of the blade assembly for magnetically attracting and thus maintaining the blade assembly in a close position with respect to the lower disk to eliminate “pump” action or axial reciprocation of the blade assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which:

[0011]FIG. 1 is a perspective view of a fan constructed in accordance with the present invention;

[0012]FIG. 2 is a cross-sectional view of the fan of the present invention with a blade assembly separated from a frame of the fan;

[0013]FIG. 3 is a cross-sectional view of the fan of the present invention;

[0014]FIG. 4 is a perspective view showing, in a separated manner, an upper silicon steel member and a lower silicon steel member of the fan of the present invention;

[0015]FIG. 5 is an assembled view of FIG. 4 with the upper and lower silicon steel members fixed together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] With reference to the drawings and in particular to FIGS. 1 and 2, a fan constructed in accordance with the present invention, generally designated with reference numeral 10, comprises a frame 20 inside which a blade assembly 11 is rotatably supported and driven by magnetically induced forces.

[0017] Also referring to FIG. 3, the blade assembly 11 comprises a hollow cylinder 13 with an end closed and a concentric axle 15 extending from the closed end of the cylinder 13. A plurality of blades 12 is mounted to and equally spaced along an outside surface of the cylinder 13. Magnet means 14 comprising at least one ring magnet is fixed to an inside surface of the cylinder 13.

[0018] The frame 20 comprises a bearing device 21 defining a central bore 22 for rotatably and snugly receiving the axle 15 therein whereby the blade assembly 11 is rotatably supported by the bearing device 21 in the frame 20. Windings of conductive wires 23 are formed around the bearing device 21. The conductive wires 23 are connected to an electrical power source (not shown) to receive electrical current therefrom. When the electrical current flows through the windings 23, a magnetic field is induced which interacts with the magnet means 14 of the blade assembly 11 to drive the blade assembly 11.

[0019] Also referring to FIGS. 4 and 5, the windings 23 are encased in a casing (not labeled) made of silicon steel. The casing is comprised of a lower member or base 40 and an upper member or cover 30 mounted together to encase the windings 23. The lower member 40 is made in the form of a circular disk defining a plurality of notches 42 equally spaced along a circumference thereof. A hub 41 is formed on the lower member 40 for receiving the bearing device 21 therein.

[0020] The upper member 30 is made in the form of a circular disk having a surface area smaller than a surface area of the lower member 40. Namely, the radius of the upper member 30 is smaller than the radius of the lower member 40. The upper member 30 defines a central hole 31 substantially aligned with the hub 41 of the lower member 40. A plurality of tabs 32 extends perpendicularly from a circumference of the upper member 30 and having free ends respectively corresponding to and fit into the notches 42 of the lower member 40. The bearing device 21 is received in both the hole 31 of the upper member 30 and the hub 41 of the lower member 40 and supported by the upper and lower members 30, 40.

[0021] Since the tabs 32 of the upper member 30 have a major surface extending in a circumferential direction of the windings 23 (namely the major surfaces of the tabs 32 defining a cylinder covering the windings 23 if the tabs 32 are extended in the circumferential direction), rather than in a radial direction as commonly observed in the conventional fan rotor, the surface area of the tabs 32 on which a driving force caused by the interaction between the magnetic field induced by the windings 23 and the magnet means 14 is effectively increased thereby substantially increasing the torque acting upon the blade assembly 11.

[0022] Since the radius of the lower member 40 is greater than that of the upper member 30, when the tabs 32 of the upper member 30 are fit into the corresponding notches 42 of the lower member 40, the portions of the lower member 40 that are between adjacent notches 42 are located beyond the tabs 32 of the upper member 30 and corresponding, in position, to the ring magnet 14. Thus, an attraction force is induced between the magnet means 14 and the lower member 40 to retain the blade assembly 11 close to the lower member 40 and consequently eliminating the so called “pump” action of the blade assembly 11. (The “pump” action of the blade assembly 11 occurs when a fan is activated and the rotor or blade assembly moves axially and reciprocally with respect to the stator or frame.)

[0023] Since the hub 41 is integrally formed on the lower member 40, additional bushing or collar is not necessary in retaining the bearing device 21 and the axle 15 in position. This simplifies the structure of the fan and reduces costs thereof.

[0024] In the embodiment illustrated, the upper member 30 has four tabs 32 which correspond to four poles of the fan. However, it is apparent to those having ordinary skills in the art to increase the number of the tabs 32 in two to count the poles number to six, eight and so on. Thus, operation stability can be easily maintained and the costs of material can be reduced.

[0025] Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims. 

What is claimed is:
 1. A fan comprising: a blade assembly comprising a cylinder having an outer surface to which blades are mounted and an inner surface to which magnet means is attached, the blade assembly comprising an axle concentric with the cylinder; and a frame rotatably supporting the blade assembly, a casing made of silicone steel being fixed in the frame and supporting a bearing device that defines a central bore rotatably receiving the axle of the blade assembly therein with the cylinder of the blade assembly fit over and spaced from the casing, windings of conductive wires being encased and fixed in the casing and surrounding the bearing device for being electrically powered to generate a magnetic field that interacts with the magnetic means of the blade assembly to rotate the blade assembly, the casing comprising opposite upper and lower disks with tabs extending between the upper and lower disks, the tabs having a major surface extending along a circumferential direction of the disks.
 2. The fan as claimed in claim 1, wherein the lower disk forms a number of notches in and spaced along a circumference thereof, the tabs being integrally formed with the upper disk and extending from a circumference of the upper disk, the tabs having free ends respectively fit into the notches of the lower disk.
 3. The fan as claimed in claim 1, wherein the upper disk defines a central hole and the lower disk forms a hub substantially aligned with the central hole of the upper disk, the bearing device being received in and retained by the central hole of the upper disk and the hub of the lower disk.
 4. The fan as claimed in claim 1, wherein the lower disk forms a plurality of portions spaced along a circumference thereof and projecting beyond the tabs, the portions being positioned in correspondence to the magnet means of the blade assembly for attracting and thus retaining the blade assembly in a close position. 